The Mechanisms And Effects Of MiR-21 Downregulating PDCD4 On Proliferation And Invasion Of Human Renal Cancer Cells

Objectives: The tumor suppressor gene entitled programmed cell death 4(PDCD4)is downregulated by micro RNA-21(mi R-21)in renal cancer.The aim of this study was to investigate the roles and interactions of PDCD4 and mi R-21 in human renal cell carcinoma(RCC)as well as the mechanism underlying the regulation of PDCD4 expression in renal cancer.Materials and methods: One renal cancer cell line(769-P)and one normal cell line(HK-2)were studied.The expression of PDCD4 protein was examined by Western-blot and q RT-PCR were performed to examine the expression levels of PDCD4 m RNA and mi R-21.Furthermore,We performed transfection of renal cancer cell line(769-P)with pre-mi R-21(mimics)and anti-mi R-21(inhibitor),then observed the expression of PDCD4 protein by westen-blot,cell proliferation by EDU and expression levels of PDCD4 m RNA by q RT-PCR.A soft agar formation assay was used to determine the effect of mi R-21,and survivin on the transformation capability of renal cancer cell(769-P).Results: Mi R-21 expression was significantly upregulated in renal cancer cell line(769-P)compared to normal cell line(HK-2)(P<0.05).In contrast,PDCD4 protein expression was significantly decreased in 769-P compared to HK-2(P<0.05),whereas the gene expression remained unaltered(P>0.05).The transfection was efficient with significantly decreased expression of mi R-21 as compared to the control,whereas PDCD4 m RNA was almost unaltered in negative control si RNA,mi R-21 mimic and mi R-21inhibitor-transfected cells(P>0.05),and there was a significant reduction of PDCD4 protein amounts in mi R-21mimic-transfected cells but significant increase in mi R-21inhibitor-transfected cells(P<0.05).In soft agar formation assays,we found a significant increase in transformation capacity in mi R-21mimic-transfected cells and a significant reduction in transformation capacity in mi R-21inhibitor-transfected cells(P<0.05).Furthermore,mi R-21mimic-transfected cells show a increased cell proliferation capacity by EDU assay,but mi R-21inhibitor-transfected cells show a inverse phenomenon(P<0.05).These data suggest that mi R-21 relates familiarly to the transformation,proliferation and metastasis of RCC and specifically downregulates PDCD4 at the post-transcriptional level,and that mi R-21 positively regulates invasion of cultured renal cancer cells.Conclusions: In our study,we observed an inverse relationship between mi R-21 and PDCD4 protein expression in RCC and our results demonstrated that mi R-21 not only promoted cancer cell hyperplasia and contributed to tumor cell transformation,invasion and metastasis,but also downregulated PDCD4 protein expression.PDCD4 and mi R-21 expression levels potentially play an important role in renal cancer.